What are crescents in kidney biopsies?
Crescent formation is a nonspecific response to severe injury of the glomerular capillary wall.
As a result, fibrin leaks into Bowman’s space, causing parietal epithelial cells to proliferate and mononuclear phagocytes to migrate into the glomerular tuft from the circulation.
Large crescents can compress glomerular capillaries and impair filtration.
Although crescent formation can resolve, some inflammatory chemotactic signals recruit fibroblasts into Bowman’s space, which ultimately can cause both the crescents and glomeruli to scar.
Extensive scarring results in end-stage kidney disease (ESKD). Similar to RPGN, crescentic nephritis is not a specific pathologic diagnosis. Crescents can be seen with a number of specific glomerular diseases
